A new polymorph of ZrO2 of an orthorhombic crystal structure (o-ZrO2) is derived in a mesoporous structure. It has average 15 nm crystallite size after 2 h of heating at 500 degreesC a mesoporous ZrO(OH)(2) . xH(2)O precursor. X-ray diffractogram determines lattice parameters of a = 0.3340 nm, b = 0.5535 nm and c = 0.6364 nm in p = 6.96 g/cm(3) density. A high-pressure phase of Pnma o-ZrO2 is known with a similar rho = 6.78 g/cm(3). Mesoporous o-ZrO2 has a strong XPS bandgroup of 3d(5/2) and 3d(3/2) components (bandwidth DeltaE(b) = 4.6 eV) at 182.7 and 184.7 eV binding energy E-b, with an additional weak bandgroup at 170-179 eV. IR spectrum infers a severely puckered structure with a corrugated surface through pores. (C) 2003 Elsevier B.V. All rights reserved.